ICAO three-letter codes are always unique. The official source, ICAO Document 8585, says the following: 1.2 The same designator will not be registered for more than one aircraft operating agency, aeronautical authority or service.

How are ICAO codes assigned?

ICAO code consists of 4 letters. Certain classifications among countries and regions are used in creating these codes. The first letter stands for the region in which the airport is located, the second is for the country. The other two letters are generally given in order.

Can two airports have the same code?

No two airports share the same IATA code, though officials say it’s possible we’ll have to rethink the process if more crop up than there are three-letter combinations to assign (this isn’t likely to happen anytime soon).